Phase lock control method and device, readable storage medium and grid-connected equipment

Abstract

The invention provides a phase lock control method and device, a readable storage medium and grid-connected equipment, and relates to the technical field of inversion control. The phase lock control method comprises the following steps: acquiring an input voltage signal and an analog filter transfer function; discretizing the transfer function of the analog filter according to the sampling period of the input voltage signal to obtain a digital filter; filtering the input voltage signal through a digital filter to obtain a filtered voltage signal; and inputting the filtered voltage signal to a phase-locked loop to determine frequency information and phase information of the input voltage signal through the phase-locked loop. According to the invention, the fluctuation of the output frequency after conversion is smaller, the detection accuracy of the frequency and the phase is improved, the total harmonic distortion of the grid-connected current is reduced, and the harmonic interference of the grid-connected equipment on the power grid is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of inverter control, and in particular to a phase-locked control method and device, a readable storage medium, and a grid-connected device. Background Art

[0002] For renewable energy grid-connected systems such as photovoltaic power generation and wind power generation, a phase-locked loop (PLL) is usually used to track the frequency and phase of the input voltage signal so that its output is consistent with the frequency and phase of the input signal. When the input voltage signal contains a DC component, the β-axis voltage will amplify the DC signal, causing the converted output voltage to contain a large sinusoidal component. This sinusoidal component will cause ripples in the output frequency, ultimately causing sinusoidal fluctuations in the phase of the phase-locked loop output, increasing the total harmonic distortion of the grid-connected current. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the related art or related art.

[0004] To this end, a first aspect of the present application proposes a phase-locked control method.

[0005] A second aspect of the present application provides a phase-locked control device.

[0006] A third aspect of the present application provides a phase-locked control device.

[0007] A fourth aspect of the present application provides a readable storage medium.

[0008] A fifth aspect of the present application provides a grid-connected device.

[0009] In view of this, the first aspect of the present application provides a phase-locked control method, which includes: obtaining an input voltage signal and an analog filter transfer function; discretizing the analog filter transfer function according to a sampling period of the input voltage signal to obtain a digital filter; filtering the input voltage signal through the digital filter to obtain a filtered voltage signal; and inputting the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop.

[0010] In this technical solution, in phase-locked control scenarios, such as photovoltaic power generation grid-connected scenarios, by tracking the phase and frequency of the grid voltage, the voltage signal output by the grid-connected device can track the frequency and phase of the input voltage signal, reducing interference to the grid. Among them, the second-order generalized integrator (SOGI) phase-locked loop has the advantages of high accuracy, good stability, fast response speed and strong anti-interference ability, so it is widely cited.

[0011] From the transfer function of the signal filtering part of the SOGI phase-locked loop, we can see that v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, v β (s) has a certain amplification effect on DC signals. When the input voltage signal contains a DC component, due to v β (s) The amplification effect on the DC component of the voltage causes the transformed output voltage to contain a large sinusoidal component, which leads to ripple in the output frequency. Therefore, the output phase of the phase-locked loop will show sinusoidal fluctuations.

[0012] To this end, the present application designs a new analog filter transfer function, and based on the new analog filter transfer function, generates a digital filter, and uses the digital filter to filter the input signal of the phase-locked loop, thereby effectively eliminating the influence of the DC signal that may be mixed therein.

[0013] Exemplarily, by designing a DC component suppression filter structure, the DC component suppression filter is an analog filter, and based on the DC component suppression filter structure, an analog filter transfer function is obtained. The analog filter transfer function is discretized to obtain a digital filter.

[0014] The collected grid voltage signal is processed by the operational amplifier circuit and analog-to-digital conversion to obtain the input signal v(z), which is then input into the digital filter for filtering to obtain the filtered voltage signal. After the filtered voltage signal is input into the phase-locked loop, the frequency and phase information of the grid signal can be obtained, thereby realizing phase-locked control.

[0015] The technical solution of the present application designs a digital filter to filter the DC signal component in the input signal, which can effectively suppress the fluctuation of the phase-locked loop output voltage vector, making the fluctuation of the converted output frequency smaller, improving the detection accuracy of frequency and phase, and helping to reduce the total harmonic distortion (THD) of the grid-connected current, thereby reducing the harmonic interference of the grid-connected equipment on the power grid.

[0016] In addition, the phase-locked control method in the above technical solution provided by the present application may also have the following additional technical features:

[0017] In some technical solutions of the present application, optionally, the analog filter transfer function is:

[0018]

[0019]

[0020] Among them, v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, [v α , v β ] is the voltage vector, k and n are constants, ω is the angular frequency of the input voltage signal, and s is the complex variable in the Laplace transform.

[0021] In the embodiment of the present application, it can be seen from the structure of the analog filter that the voltage vector [v α , v β As shown in the above formula (1) and formula (2). Wherein, k is a constant, and exemplarily, satisfies 0<k<1. Exemplarily, the value of k is 0.5. n is a constant, and exemplarily, satisfies 0<n<1. Exemplarily, the value of n is 0.25. Exemplarily, the value of n is 0.125.

[0022] The present application designs a new analog filter structure and generates a digital filter based on the analog filter transfer function, thereby effectively suppressing the DC component in the input voltage signal, reducing the fluctuation of the output voltage vector, and thus reducing the THD of the grid-connected current.

[0023] In some technical solutions of the present application, optionally, the analog filter transfer function is discretized according to the sampling period of the input voltage signal, including:

[0024] The analog filter transfer function is discretized by the following formula:

[0025]

[0026] Among them, T s is the sampling period, s is the complex variable in Laplace transform, and z is the complex frequency variable in discrete time system.

[0027] In the embodiment of the present application, bilinear transformation is a method for converting an analog filter into a digital filter, which can ensure that the frequency response will not be aliased during the conversion process. By discretizing the analog filter through bilinear transformation, a digital filter can be obtained.

[0028] For example, for the analog filter transfer function v α (s) and v β (s), the transfer function in the s domain is converted into the transfer function in the z domain by using the above formula (3), thus obtaining the digital filter v α (z) and v β (z). The input voltage signal v(z) passes through the digital filter v α (z) and v β(z), the voltage output of the α-axis and β-axis can be obtained, that is, U α (z) and U β (z).

[0029] This application discretizes the analog filter transfer function through bilinear transformation to obtain the digital filter v α (z) and v β (z), the digital filter can effectively suppress the DC signal component in the input signal and reduce the fluctuation of the phase of the phase-locked loop output.

[0030] In some technical solutions of the present application, optionally, the filtered voltage signal includes an α-axis voltage and a β-axis voltage; before inputting the filtered voltage signal into the phase-locked loop, the phase-locked control method further includes: performing Park transformation processing on the α-axis voltage and the β-axis voltage.

[0031] In this technical solution, after passing through the digital filter v α (z) and v β (z) After filtering the input voltage signal v(z), the α-axis voltage output U can be obtained. α (z) and β-axis voltage output U β (z). Output the α-axis voltage to U α (z) and β-axis voltage output U β (z) After Parker transformation (dq transformation), the output vector [U d , U q ] has smaller fluctuations, through [U d , U q ]Frequency detection of the phase-locked loop can make the detected frequency information more accurate, reduce the THD of the grid-connected current, and reduce the harmonic interference of grid-connected equipment such as inverters to the grid.

[0032] In some technical solutions of the present application, optionally, after inputting the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop, the phase-locked control method also includes: updating the filtering parameters of the digital filter based on the frequency information of the input voltage signal determined by the phase-locked loop.

[0033] In this technical solution, it can be seen from the above formulas (1), (2) and (3) that the digital filter v α (z) and v β (z) contains the angular frequency parameter ω. α (z) and v β (z) Get the α-axis voltage output U α (z) and β-axis voltage output U β (z), then perform Parker transformation (dq transformation) to obtain the output vector [Ud , U q ].

[0034] Among them, the q-axis component U q As the input source signal of the phase-locked loop, after the proportional integral (PI) correction link, the inherent angular frequency ω is superimposed n After that, the input angular frequency of the filter is obtained, which is recorded as angular frequency ω1. This new angular frequency is used to update the filter coefficient ω1.

[0035] For example, the above natural angular frequency ω n is related to the frequency of the grid voltage signal. For example, assuming that the frequency of the grid voltage signal is 50 Hz, then ω n The value of is 100π.

[0036] In some technical solutions of the present application, optionally, obtaining an input voltage signal includes: collecting a grid voltage signal; wherein the grid voltage signal is an analog signal; amplifying the grid voltage signal to obtain an amplified signal; and performing analog-to-digital conversion on the amplified signal to obtain an input voltage signal.

[0037] In the technical solution of the present application, the grid voltage signal of the input signal is collected through the voltage sampling module, and the grid voltage signal is first amplified by the amplifier circuit. The operational amplifier circuit can realize the conditioning function of the input signal, and convert the grid voltage signal with DC interference and harmonic interference into an input signal allowed by the analog to digital converter (ADC), that is, the above-mentioned amplified signal. After obtaining the amplified signal, the amplified signal is input into the analog to digital converter for analog-to-digital conversion to obtain the above-mentioned input voltage signal v(z).

[0038] The second aspect of the present application provides a phase-locked control device, which includes: an acquisition module, used to acquire an input voltage signal and an analog filter transfer function; a processing module, used to discretize the analog filter transfer function according to a sampling period of the input voltage signal to obtain a digital filter; and filter the input voltage signal through the digital filter to obtain a filtered voltage signal; a phase-locked loop module, used to input the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop.

[0039] In this technical solution, in phase-locked control scenarios, such as photovoltaic power generation grid-connected scenarios, by tracking the phase and frequency of the grid voltage, the voltage signal output by the grid-connected device can track the frequency and phase of the input voltage signal, reducing interference to the grid. Among them, the second-order generalized integrator (SOGI) phase-locked loop has the advantages of high accuracy, good stability, fast response speed and strong anti-interference ability, so it is widely cited.

[0040] From the transfer function of the signal filtering part of the SOGI phase-locked loop, we can see that v β (s) has a certain amplification effect on DC signals. When the input voltage signal contains a DC component, due to v β (s) The amplification effect on the DC component of the voltage causes the transformed output voltage to contain a large sinusoidal component, which leads to ripple in the output frequency. Therefore, the output phase of the phase-locked loop will show sinusoidal fluctuations.

[0041] To this end, the present application designs a new analog filter transfer function, and based on the new analog filter transfer function, generates a digital filter, and uses the digital filter to filter the input signal of the phase-locked loop, thereby effectively eliminating the influence of the DC signal that may be mixed therein.

[0042] Exemplarily, by designing a DC component suppression filter structure, the DC component suppression filter is an analog filter, and based on the DC component suppression filter structure, an analog filter transfer function is obtained. The analog filter transfer function is discretized to obtain a digital filter.

[0043] The collected grid voltage signal is processed by the operational amplifier circuit and analog-to-digital conversion to obtain the input signal v(z), which is then input into the digital filter for filtering to obtain the filtered voltage signal. After the filtered voltage signal is input into the phase-locked loop, the frequency and phase information of the grid signal can be obtained, thereby realizing phase-locked control.

[0044] The technical solution of the present application designs a digital filter to filter the DC signal component in the input signal, which can effectively suppress the fluctuation of the phase-locked loop output voltage vector, making the fluctuation of the converted output frequency smaller, improving the detection accuracy of frequency and phase, and helping to reduce the total harmonic distortion (THD) of the grid-connected current, thereby reducing the harmonic interference of the grid-connected equipment on the power grid.

[0045] The third aspect of the present application provides a phase-locked control device, which includes: a memory, the memory is used to store programs or instructions; a processor, the processor is used to implement the steps of the phase-locked control method provided in any of the above technical solutions when executing the programs or instructions, and therefore also includes all the beneficial effects of the phase-locked control method provided in any of the above technical solutions. To avoid repetition, they will not be repeated here.

[0046] In a fourth aspect, the present application provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the phase-locked control method provided in any of the above technical solutions are implemented, and therefore all the beneficial effects of the phase-locked control method provided in any of the above technical solutions are also included. To avoid repetition, they will not be repeated here.

[0047] The fifth aspect of the present application provides a grid-connected device, which includes: a phase-locked control device as provided in any of the above-mentioned technical solutions; and / or a readable storage medium as provided in any of the above-mentioned technical solutions. Therefore, the grid-connected device also includes all the beneficial effects of the phase-locked control device as provided in any of the above-mentioned technical solutions and / or the readable storage medium as provided in any of the above-mentioned technical solutions. To avoid repetition, they will not be repeated here.

[0048] Illustratively, the grid-connected equipment proposed in this application includes, but is not limited to, inverters, photovoltaic power generation strings, and wind power generation equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0050] Figure 1 A flow chart showing a phase-locked control method according to some embodiments of the present application is shown;

[0051] Figure 2 A schematic diagram of an output phase of a phase-locked loop in the related art is shown;

[0052] Figure 3 A schematic diagram showing the output phase of a phase-locked loop in some embodiments of the present application is shown;

[0053] Figure 4 A schematic diagram showing the structure of an analog filter in some embodiments of the present application is shown;

[0054] Figure 5 A schematic diagram showing the structure of a phase-locked loop in some embodiments of the present application is shown;

[0055] Figure 6 A schematic diagram showing a phase-locked loop system of some embodiments of the present application is shown;

[0056] Figure 7 A structural block diagram of a phase-locked control device according to some embodiments of the present application is shown;

[0057] Figure 8 A structural block diagram of a phase-locked control device according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0058] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0059] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0060] Refer to the following Figures 1 to 8 The present invention describes a phase-locked control method and apparatus, a readable storage medium, and a grid-connected device according to some embodiments of the present application.

[0061] In some embodiments of the present application, a phase-locked control method is provided. Figure 1 A flow chart of a phase-locked control method according to some embodiments of the present application is shown. Figure 1 As shown, the phase-locked control method includes:

[0062] Step 102, obtaining an input voltage signal and an analog filter transfer function;

[0063] Step 104, discretizing the analog filter transfer function according to the sampling period of the input voltage signal to obtain a digital filter;

[0064] Step 106, filtering the input voltage signal through a digital filter to obtain a filtered voltage signal;

[0065] Step 108: input the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop.

[0066] In this embodiment, in a phase-locked control scenario, such as a photovoltaic power generation grid-connected scenario, by tracking the phase and frequency of the grid voltage, the voltage signal output by the grid-connected device can track the frequency and phase of the input voltage signal, thereby reducing interference to the grid. Among them, the second-order generalized integrator (SOGI) phase-locked loop has the advantages of high precision, good stability, fast response speed and strong anti-interference ability, and is therefore widely cited.

[0067] From the transfer function of the signal filtering part of the SOGI phase-locked loop, we can see that v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, v β (s) has a certain amplification effect on DC signals. When the input voltage signal contains a DC component, due to v β (s) The amplification effect on the DC component of the voltage causes the transformed output voltage to contain a large sinusoidal component, which leads to ripple in the output frequency. Therefore, the output phase of the phase-locked loop will show sinusoidal fluctuations.

[0068] To this end, the present application designs a new analog filter transfer function, and based on the new analog filter transfer function, generates a digital filter, and uses the digital filter to filter the input signal of the phase-locked loop, thereby effectively eliminating the influence of the DC signal that may be mixed therein.

[0069] Exemplarily, by designing a DC component suppression filter structure, the DC component suppression filter is an analog filter, and based on the DC component suppression filter structure, an analog filter transfer function is obtained. The analog filter transfer function is discretized to obtain a digital filter.

[0070] The collected grid voltage signal is processed by the operational amplifier circuit and analog-to-digital conversion to obtain the input signal v(z), which is then input into the digital filter for filtering to obtain the filtered voltage signal. After the filtered voltage signal is input into the phase-locked loop, the frequency and phase information of the grid signal can be obtained, thereby realizing phase-locked control.

[0071] Figure 2 Schematic diagram of the output phase of a phase-locked loop in the related art is shown. Figure 2 As shown, since the input signal v contains a DC component, the obtained U d , U q The fluctuation is larger. Figure 3 Schematic diagram of output phase of the phase-locked loop of some embodiments of the present application is shown, such as Figure 3 As shown, by filtering the DC component in the input signal v, U can be effectively reduced. d , U q The fluctuation makes the frequency detection more accurate.

[0072] The embodiment of the present application designs a digital filter to filter the DC signal component in the input signal, which can effectively suppress the fluctuation of the phase-locked loop output voltage vector, make the fluctuation of the converted output frequency smaller, improve the detection accuracy of frequency and phase, and help reduce the total harmonic distortion (THD) of the grid-connected current, thereby reducing the harmonic interference of the grid-connected equipment to the power grid.

[0073] In some embodiments of the present application, optionally, the analog filter transfer function is:

[0074]

[0075] Among them, v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, [v α , v β ] is the voltage vector, k and n are constants, ω is the angular frequency of the input voltage signal, and s is the complex variable in the Laplace transform.

[0076] In the embodiments of the present application, Figure 4 The schematic diagram of the structure of the analog filter of some embodiments of the present application is shown as follows: Figure 4 As shown in the figure, from the structure of the analog filter, it can be seen that the voltage vector [v α , v β As shown in the above formula (1) and formula (2). Wherein, s is the target tracking frequency, k is a constant, and exemplarily, 0<k<1 is satisfied. Exemplarily, the value of k is 0.5. n is a constant, and exemplarily, 0<n<1 is satisfied. Exemplarily, the value of n is 0.25. Exemplarily, the value of n is 0.125.

[0077] The present application designs a new analog filter structure and generates a digital filter based on the analog filter transfer function, thereby effectively suppressing the DC component in the input voltage signal, reducing the fluctuation of the output voltage vector, and thus reducing the THD of the grid-connected current.

[0078] In some embodiments of the present application, optionally, discretization processing is performed on the analog filter transfer function according to the sampling period of the input voltage signal, including:

[0079] The analog filter transfer function is discretized by the following formula:

[0080]

[0081] Among them, T s is the sampling period, s is the complex variable in Laplace transform, and z is the complex frequency variable in discrete time system.

[0082] In the embodiment of the present application, bilinear transformation is a method for converting an analog filter into a digital filter, which can ensure that the frequency response will not be aliased during the conversion process. By discretizing the analog filter through bilinear transformation, a digital filter can be obtained.

[0083] For example, for the analog filter transfer function v α (s) and v β (s), the transfer function of the s plane is converted into the transfer function of the z plane through the above formula (3), so as to obtain the digital filter v α (z) and v β (z). The input voltage signal v(z) passes through the digital filter v α (z) and v β (z), the voltage output of the α-axis and β-axis can be obtained, that is, U α (z) and U β (z).

[0084] This application discretizes the analog filter transfer function through bilinear transformation to obtain the digital filter v α (z) and v β (z), the digital filter can effectively suppress the DC signal component in the input signal and reduce the fluctuation of the phase of the phase-locked loop output.

[0085] In some embodiments of the present application, optionally, the filtered voltage signal includes an α-axis voltage and a β-axis voltage; before inputting the filtered voltage signal into the phase-locked loop, the phase-locked control method further includes: performing Park transformation processing on the α-axis voltage and the β-axis voltage.

[0086] In this embodiment, after passing through the digital filter v α (z) and v β (z) After filtering the input voltage signal v(z), the α-axis voltage output U can be obtained. α (z) and β-axis voltage output U β (z). Output the α-axis voltage to U α (z) and β-axis voltage output U β (z) After Parker transformation (dq transformation), the output vector [U d , U q ] has smaller fluctuations, through [U d , U q ]Frequency detection of the phase-locked loop can make the detected frequency information more accurate, reduce the THD of the grid-connected current, and reduce the harmonic interference of grid-connected equipment such as inverters to the grid.

[0087] For example, Figure 5The structure diagram of the phase-locked loop of some embodiments of the present application is shown as follows: Figure 5 As shown, where v α and v β They are the α-axis voltage signal and the β-axis voltage signal respectively. After dq conversion, the d-axis voltage U is output. d and q-axis voltage U q , where the q-axis component U q As the input source signal of the phase-locked loop, after the proportional integral (PI) correction link, the inherent angular frequency ω is superimposed n After that, the frequency ω and phase θ of the signal are obtained.

[0088] In some embodiments of the present application, optionally, after inputting the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop, the phase-locked control method further includes: updating the filtering parameters of the digital filter based on the frequency information of the input voltage signal determined by the phase-locked loop.

[0089] In this embodiment, it can be known from the above formulas (1), (2) and (3) that the digital filter v α (z) and v β (z) contains the angular frequency parameter ω. α (z) and v β (z) Get the α-axis voltage output U α (z) and β-axis voltage output U β (z), then perform Parker transformation (dq transformation) to obtain the output vector [U d , U q ].

[0090] Among them, the q-axis component U q As the input source signal of the phase-locked loop, after the proportional integral (PI) correction link, the inherent angular frequency ω is superimposed n After that, the input angular frequency of the filter is obtained, which is recorded as angular frequency ω1. This new angular frequency is used to update the filter coefficient ω1.

[0091] For example, the above natural angular frequency ω n is related to the frequency of the grid voltage signal. For example, assuming that the frequency of the grid voltage signal is 50 Hz, then ω n The value of is 100π.

[0092] The present application can dynamically update the filter coefficients to achieve closed-loop control, while improving the digital filter's ability to filter out DC signals.

[0093] In some embodiments of the present application, optionally, obtaining an input voltage signal includes: collecting a grid voltage signal; wherein the grid voltage signal is an analog signal; amplifying the grid voltage signal to obtain an amplified signal; and performing analog-to-digital conversion on the amplified signal to obtain an input voltage digital signal.

[0094] In the embodiments of the present application, Figure 6 A schematic diagram of a phase-locked loop system of some embodiments of the present application is shown. Figure 6 As shown in the figure, the grid voltage signal contains interference signals. After being processed by the amplifier circuit, this part of the signal is input to the digital signal controller. After AD conversion by the analog-to-digital converter, the digital signal V is obtained. After the digital signal V is processed by the digital filter, the α-axis signal v is output. α and the β axis signal v β , after being processed by the phase-locked loop, the frequency ω and phase θ of the output signal.

[0095] The voltage sampling module collects the grid voltage signal of the input signal, and the grid voltage signal is first amplified by the amplifier circuit. The operational amplifier circuit can realize the conditioning function of the input signal, and convert the grid voltage signal with DC interference and harmonic interference into an input signal allowed by the analog to digital converter (ADC), that is, the above-mentioned amplified signal. After obtaining the amplified signal, the amplified signal is input into the analog to digital converter for analog-to-digital conversion to obtain the above-mentioned input voltage signal v(z).

[0096] In some embodiments of the present application, a phase-locked control device is provided. Figure 7 The structure block diagram of the phase-locked control device of some embodiments of the present application is shown as follows: Figure 7 As shown, the phase-locked control device 700 includes:

[0097] The acquisition module 702 is used to acquire the input voltage signal and the analog filter transfer function; the processing module 704 is used to discretize the analog filter transfer function according to the sampling period of the input voltage signal to obtain a digital filter; and filter the input voltage signal through the digital filter to obtain a filtered voltage signal; the phase-locked loop module 706 is used to input the filtered voltage signal into the phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop; the control module 708 is used to perform phase-locked control based on the frequency information and phase information.

[0098] In this embodiment, in a phase-locked control scenario, such as a photovoltaic power generation grid-connected scenario, by tracking the phase and frequency of the grid voltage, the voltage signal output by the grid-connected device can track the frequency and phase of the input voltage signal, thereby reducing interference to the grid. Among them, the second-order generalized integrator (SOGI) phase-locked loop has the advantages of high precision, good stability, fast response speed and strong anti-interference ability, and is therefore widely cited.

[0099] From the transfer function of the signal filtering part of the SOGI phase-locked loop, we can see that v β (s) has a certain amplification effect on DC signals. When the input voltage signal contains a DC component, due to v β (s) The amplification effect on the DC component of the voltage causes the transformed output voltage to contain a large sinusoidal component, which leads to ripple in the output frequency. Therefore, the output phase of the phase-locked loop will show sinusoidal fluctuations.

[0100] To this end, the present application designs a new analog filter transfer function, and based on the new analog filter transfer function, generates a digital filter, and uses the digital filter to filter the input signal of the phase-locked loop, thereby effectively eliminating the influence of the DC signal that may be mixed therein.

[0101] Exemplarily, by designing a DC component suppression filter structure, the DC component suppression filter is an analog filter, and based on the DC component suppression filter structure, an analog filter transfer function is obtained. The analog filter transfer function is discretized to obtain a digital filter.

[0102] The collected grid voltage signal is processed by the operational amplifier circuit and analog-to-digital conversion to obtain the input signal v(z), which is then input into the digital filter for filtering to obtain the filtered voltage signal. After the filtered voltage signal is input into the phase-locked loop, the frequency and phase information of the grid signal can be obtained, thereby realizing phase-locked control.

[0103] The embodiment of the present application designs a digital filter to filter the DC signal component in the input signal, which can effectively suppress the fluctuation of the phase-locked loop output voltage vector, make the fluctuation of the converted output frequency smaller, improve the detection accuracy of frequency and phase, and help reduce the total harmonic distortion (THD) of the grid-connected current, thereby reducing the harmonic interference of the grid-connected equipment to the power grid.

[0104] In some embodiments of the present application, optionally, the analog filter transfer function is:

[0105]

[0106] Among them, v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, [v α , v β ] is the voltage vector, k and n are constants, ω is the frequency information of the input voltage signal, and s is the complex variable in the Laplace transform.

[0107] In the embodiment of the present application, it can be seen from the structure of the analog filter that the voltage vector [v α , v β As shown in the above formula (1) and formula (2). Wherein, s is the target tracking frequency, k is a constant, and exemplarily, 0<k<1 is satisfied. Exemplarily, the value of k is 0.5. n is a constant, and exemplarily, 0<n<1 is satisfied. Exemplarily, the value of n is 0.25. Exemplarily, the value of n is 0.125.

[0108] The present application designs a new analog filter structure and generates a digital filter based on the analog filter transfer function, thereby effectively suppressing the DC component in the input voltage signal, reducing the fluctuation of the output voltage vector, and thus reducing the THD of the grid-connected current.

[0109] In some embodiments of the present application, optionally, the processing module is further configured to discretize the analog filter transfer function using the following formula:

[0110]

[0111] Among them, T s is the sampling period, s is the complex variable in Laplace transform, and z is the complex frequency variable in discrete time system.

[0112] In the embodiment of the present application, bilinear transformation is a method for converting an analog filter into a digital filter, which can ensure that the frequency response will not be aliased during the conversion process. By discretizing the analog filter through bilinear transformation, a digital filter can be obtained.

[0113] For example, for the analog filter transfer function v α (s) and v β (s), the transfer function in the s domain is converted into the transfer function in the z domain by using the above formula (3), thus obtaining the digital filter v α (z) and v β (z). The input voltage signal v(z) passes through the digital filter v α (z) and v β (z), the voltage output of the α-axis and β-axis can be obtained, that is, Uα (z) and U β (z).

[0114] This application discretizes the analog filter transfer function through bilinear transformation to obtain the digital filter v α (z) and v β (z), the digital filter can effectively suppress the DC signal component in the input signal and reduce the fluctuation of the phase of the phase-locked loop output.

[0115] In some embodiments of the present application, optionally, the filtered voltage signal includes an α-axis voltage and a β-axis voltage; the processing module is further used to perform Park transformation processing on the α-axis voltage and the β-axis voltage.

[0116] In this embodiment, after passing through the digital filter v α (z) and v β (z) After filtering the input voltage signal v(z), the α-axis voltage output U can be obtained. α (z) and β-axis voltage output U β (z). Output the α-axis voltage to U α (z) and β-axis voltage output U β (z) After Parker transformation (dq transformation), the output vector [U d , U q ] has smaller fluctuations, through [U d , U q ]Frequency detection of the phase-locked loop can make the detected frequency information more accurate, reduce the THD of the grid-connected current, and reduce the harmonic interference of grid-connected equipment such as inverters to the grid.

[0117] In some embodiments of the present application, optionally, the phase-locked control device further includes: an updating module, configured to update filtering parameters of the digital filter based on frequency information of the input voltage signal determined by the phase-locked loop.

[0118] In this embodiment, it can be known from the above formulas (1), (2) and (3) that the digital filter v α (z) and v β (z) contains the angular frequency parameter ω. α (z) and v β (z) Get the α-axis voltage output U α (z) and β-axis voltage output U β (z), then perform Parker transformation (dq transformation) to obtain the output vector [U d , U q ].

[0119] Among them, the q-axis component U qAs the input source signal of the phase-locked loop, after the proportional integral (PI) correction link, the inherent angular frequency ω is superimposed n After that, the input angular frequency of the filter is obtained, which is recorded as angular frequency ω1. This new angular frequency is used to update the filter coefficient ω1.

[0120] For example, the above natural angular frequency ω n is related to the frequency of the grid voltage signal. For example, assuming that the frequency of the grid voltage signal is 50 Hz, then ω n The value of is 100π.

[0121] The present application can dynamically update the filter coefficients to achieve closed-loop control, while improving the digital filter's ability to filter out DC signals.

[0122] In some embodiments of the present application, optionally, the acquisition module is also used to collect a grid voltage signal; wherein the grid voltage signal is an analog signal; the processing module is also used to amplify the grid voltage signal to obtain an amplified signal; and perform analog-to-digital conversion on the amplified signal to obtain an input voltage signal.

[0123] In the embodiment of the present application, the grid voltage signal contains interference signals. This part of the signal is processed by the amplification circuit and input to the digital signal controller, wherein the digital signal V is obtained after AD conversion by the analog-to-digital converter. The digital signal V is processed by the digital filter and the α-axis signal v is output. α and the β axis signal v β , after being processed by the phase-locked loop, the frequency ω and phase θ of the output signal.

[0124] The voltage sampling module collects the grid voltage signal of the input signal, and the grid voltage signal is first amplified by the amplifier circuit. The operational amplifier circuit can realize the conditioning function of the input signal, and convert the grid voltage signal with DC interference and harmonic interference into an input signal allowed by the analog to digital converter (ADC), that is, the above-mentioned amplified signal. After obtaining the amplified signal, the amplified signal is input into the analog to digital converter for analog-to-digital conversion to obtain the above-mentioned input voltage signal v(z).

[0125] The present application can improve the accuracy of phase-locked control by performing signal amplification and analog-to-digital conversion processing on the grid voltage signal.

[0126] In some embodiments of the present application, a phase-locked control device is provided. Figure 8 The structure block diagram of the phase-locked control device of some embodiments of the present application is shown as follows: Figure 8As shown, the phase-locked control device 800 includes: a memory 802, the memory 802 is used to store programs or instructions; a processor 804, the processor 804 is used to implement the steps of the phase-locked control method provided in any of the above embodiments when executing the program or instructions, and therefore also includes all the beneficial effects of the phase-locked control method provided in any of the above embodiments, which will not be repeated here to avoid repetition.

[0127] In some embodiments of the present application, a readable storage medium is provided, on which a program or instruction is stored. When the program or instruction is executed by a processor, the steps of the phase-locked control method provided in any of the above embodiments are implemented, and therefore all the beneficial effects of the phase-locked control method provided in any of the above embodiments are also included. To avoid repetition, they will not be repeated here.

[0128] In some embodiments of the present application, a grid-connected device is provided, and the grid-connected device includes: a phase-locked control device as provided in any of the above embodiments; and / or a readable storage medium as provided in any of the above embodiments. Therefore, the grid-connected device may also include all the beneficial effects of the phase-locked control device as provided in any of the above embodiments and / or the readable storage medium as provided in any of the above embodiments. To avoid repetition, they are not repeated here.

[0129] Illustratively, the grid-connected equipment proposed in this application includes, but is not limited to, inverters, photovoltaic power generation strings, and wind power generation equipment.

[0130] The methods may be implemented in a variety of different ways depending on the specific features and / or example applications. For example, the methods may be implemented by a combination of hardware, firmware, and / or software. For example, in a hardware implementation, the processor may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, electronic devices, other device units for performing the above functions, and / or combinations thereof.

[0131] A computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer readable storage medium may be an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above devices, but is not limited thereto. A non-exhaustive list of more specific examples of computer readable storage media includes: portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory card, floppy disk, encoding mechanical device (such as a punch card or a groove with a raised structure with instructions recorded) and any suitable combination of the above devices. The computer readable storage medium used herein should not be understood as a transmission signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium, or an electrical signal transmitted through a wire, etc.

[0132] In the description of this application, the term "plurality" refers to two or more than two. Unless otherwise clearly defined, the terms "upper" and "lower" indicate positions or positional relationships based on the positions or positional relationships described in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. The terms "connect", "install", "fixed", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0133] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0134] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phase-locked control method, characterized in that: The phase-locked control method comprises: Get input voltage signal and simulate filter transfer function; According to the sampling period of the input voltage signal, the analog filter transfer function is discretized to obtain a digital filter; Filtering the input voltage signal through the digital filter to obtain a filtered voltage signal; The filtered voltage signal is input into a phase-locked loop, so as to determine the frequency information and the phase information of the input voltage signal through the phase-locked loop.

2. The phase-locked control method according to claim 1, characterized in that: The analog filter transfer function is: Among them, v α (s) is the α-axis transfer function, v β (s) is the β-axis transfer function, [v α , v β ] is the voltage vector, k and n are constants, ω is the angular frequency of the input voltage signal, and s is the complex variable in Laplace transform.

3. The phase-locked control method according to claim 2, characterized in that: The discretization processing of the analog filter transfer function according to the sampling period of the input voltage signal comprises: The analog filter transfer function is discretized by the following formula: Among them, T s is the sampling period, s is the complex variable in Laplace transform, and z is the complex frequency variable in the discrete time system.

4. The phase-locked control method according to claim 1, characterized in that: The filtered voltage signal includes an α-axis voltage and a β-axis voltage; before inputting the filtered voltage signal into the phase-locked loop, the phase-locked control method further includes: The α-axis voltage and the β-axis voltage are subjected to Park transformation processing.

5. The phase-locked control method according to claim 4, characterized in that: After inputting the filtered voltage signal into a phase-locked loop to determine the frequency information and phase information of the input voltage signal through the phase-locked loop, the phase-locked control method further includes: Based on the frequency information of the input voltage signal determined by the phase-locked loop, the filtering parameters of the digital filter are updated.

6. The phase-locked control method according to any one of claims 1 to 5, characterized in that: The step of obtaining an input voltage signal comprises: Collecting a grid voltage signal; wherein the grid voltage signal is an analog signal; Amplifying the grid voltage signal to obtain an amplified signal; The amplified signal is subjected to analog-to-digital conversion processing to obtain the input voltage signal.

7. A phase-locked control device, characterized in that: The phase-locked control device comprises: An acquisition module, used for acquiring an input voltage signal and a transfer function of an analog filter; a processing module, configured to discretize the analog filter transfer function according to a sampling period of the input voltage signal to obtain a digital filter; and Filtering the input voltage signal through the digital filter to obtain a filtered voltage signal; The phase-locked loop module is used to input the filtered voltage signal into a phase-locked loop, so as to determine the frequency information and phase information of the input voltage signal through the phase-locked loop.

8. A phase-locked control device, characterized in that: The phase-locked control device comprises: A memory, wherein the memory is used to store programs or instructions; A processor, wherein the processor is used to implement the steps of the phase-locked control method according to any one of claims 1 to 6 when executing the program or instruction.

9. A readable storage medium having a program or instruction stored thereon, characterized in that: When the program or instruction is executed by a processor, the steps of the phase-locked control method according to any one of claims 1 to 6 are implemented.

10. A grid-connected device, characterized in that: The grid-connected equipment includes: The phase-locked control device according to claim 7 or 8; and / or The readable storage medium as claimed in claim 9.

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